To calculate your pregnancy weeks after having sex during ovulation, you need to consider both your last period and the ovulation date. Typically, pregnancy is counted from the first day of your last menstrual period (LMP). However, if you know the exact date of ovulation, you can also use that as a reference point.
If your last period was on 28/12/2021 and your ovulation dates were between 9th to 12th of January, you can estimate that conception likely occurred around those days. Counting from the first day of your last period, you can calculate how old your pregnancy is.
Keep in mind that this method provides an estimate and may not be entirely accurate. It's best to consult with a healthcare professional who can perform an ultrasound or other tests to determine the gestational age more precisely.
Remember that every pregnancy is unique, and individual factors can affect the accuracy of calculations. It's always advisable to seek medical guidance for personalized information regarding your specific situation.